Slipper pump



w. T. LIVERMORE ETAL 3,009,420

Nov. 21, 1961 SLIPPER PUMP 2 Sheets-Sheet 1 Filed July 11, 1957 ,m/id

Nov. 21, 1961 w. T. LIVERMORE EI'AL 3,

SLIPPER PUMP Filed July 11, 1957 2 Sheets-Sheet 2 miuzin ATTOR/VE dUnited States Patent O M 3,009,420 SLIPPER PUMP William T. Livermore,Fort Lauderdale, Fla., and Hubert M. Clark, Birmingham, and Gilbert H.Drutchas, Detroit, Mich.; said Clark and said Drutchas assignors, bymesne assignments, to Thompson Ramo Wooldridge Inc., Cleveland, Ohio, acorporation of Ohio Filed July 11, 1957, Ser. No. 671,273 4 Claims. (Cl.103-135) This invention relates to a pump assembly and, moreparticularly, to a slipper pump of the general type disclosed incopending application Serial No. 490,288 of William T. Livermore.

Such prior application discloses a pump and valve assembly adapted tomeet the requirements of an automotive power steering pump wherein apump rotor operates to provide a seal between the inlet and outlet port.End,

plates having bearings for the rotor shaft are bolted and doweled to acenter housing enclosing the pump rotor, slippers and pump bore, and inorder to effect a satisfactory sealing relation between the rotor andpump bore, notwithstanding commercial tolerances, a procedure isdisclosed for machining the dowel holes at assembly.

The present improved construction eliminate the necessity for any directsealing relationship between the rotor and bore by employing theslippers as sealing elements in the sealing are as well as the workingarc of the pump, thereby eliminating the necessity for highly accurateradial location of the rotor in the pump bore. It further employs ablind-ended bore housing" construction with an insert sleeve containingthe pump bore andports together with a header insert containing one ofthe rotor shaft bearings. With this construction, it is possible tomachine all primary locating surfaces for the rotor shaft bearings andbore insert as concentric cylindrical surfaces in a single setup as wellas one of the header walls for the inner end of the rotor. r

In addition, the present pump incorporates. simple U-channel-shapedsheet metal slippers which may be readily formed by stamping orroll-forming operations in place of previous solid metal slippers, Inaddition to cost advantages, such slipper construction materiallydecreases the weight of the slippers and resulting centrifugal forcescontributing to bore wear, as well as providingsomewhat flexible pumpingelements capable of utilizing internal pressures to reduce sealingclearances with the rotor notches, and thus facilitate slipper sealingin the sealing arc. The present construction further provides auxiliarypassages for filling the rotor slots under the slippers, minmizing anytendency for the slippers to hang up in the slots out of contact withthe bore due to restrictions in the speed of filling during slippertravel in the intake are.

From the above brief description it will be understood that one of theobjects of the present invention is to provide a simplified, one-pieceblind bore housing construction materially reducing and simplifyingmachining operations.

' Another object is to provide a construction eliminating the necessityfor assembling the rotor in direct sealing relation with the pump bore.

Another object is to adapt slippers to provide a seal j filling therotor slots under the slippers during 15 3,009,420 Patented Nov. 21,1961 between inlet and outlet ports in the sealing are, as well asworking arc of the pump.

Another object is to provide an improved U-shapedchannel slipperconstruction adapted for construction by sheet metal stamping orroll-forming operations.

Another object is to provide a pump bore insert construction'incorporating inlet and outlet ports, a noncircular eccentric pump boresurface and a circular outer surface. I p 1 Another object is to provideU-channel-shaped slippers having radial slots for passage of oil fromthe ports to the space between the slipper and the rotor slots.

Another object is to provide auxiliary passages for the'intake cycle.,

Another object is to provide channel-shaped slippers flexible enough tobe expanded by oil pressure within the channel to reduce sealingclearances between both legs of the channel and the sides of the rotorslots.

Another object is to provide notches in the leading edge of the rotorslots deep enough to conduct pressure to the space inside the slippersafter initial outward radial displacement, but not deep enough tobreak'the seal between the leading slipper legs and the rotor slotsduring'their travel in the sealing arc.

These and other objects will be more apparent from the followingdetailed description of a preferred embodi- V mentof the present pumpand by reference to the draw- FIG. 2 is a sectional endjelevation takenalon gthe 35 line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional view of the control valve taken alongthe line 3-3 of FIG. 1;

FIG. 4 'is an enlarged fragmentary view of the pump rotor, slippers andbore with the rotor and slippers displaced to a different position fromthat shown in FIG- 2; FIG. 5 is anvend elevation of the pump assemblytaken along the line 55 of FIG. 1;

FIG. 6 is an enlarged sectional view of a modified slipper form; and

FIG. 7 is a face view of such modified slipper form,

With reference to FIG. 1 of the drawings, the pre-; ferred embodiment ofthe present invention includes a pump housing 21 mounted inside of afluid reservoir 22 and secured thereto by bolts 23 passing throughmounting bracket 24, the pump housing being adaptedwith an annularflange 25 and sealing ring 26 to form a fluidtight closure for thereservoir which is filled with hydraulic fluid through cap 27.

The pump housing is provided with three concentric cylindrical bores28a, 28b and 280 forming the seats, respectively, for rotor shaftbearing 29, a pump bore insert 30, and a front bearing insert 31, thelatter being 'held in position by snap ring 32 and sealed by ring 33 iand shaft seal 34- against any pump leakage from within the pumphousing. A rotor drive shaft 36 is drivingly connected by key 37, to thepump rotor 38, the rotor shaft being straddle mounted in bearings 29 and"39 for rotation about an axis coinciding with that of bores 28a, 28band 280.

Header surfaces for the pump rotor 38 are provided by the end 40 of thehousing bore 28b and the end 41 of the bearing insert 31, respectively.The pump 'bore insert 30 is in the form of a sleeve having a cylindricalouter surface adapted for press fit within the housing bore 28b, aneccentric inner surface forming the pump bore per se (later described indetail), an inlet port 42 and an outletport 43, as shown in FIGS. 2 and4, said for respective communication with an inlet port 44 and outletport 45 in the pump housing 21.

A cylindrical valve bore 46 in the housing intersects ports 44 and 45. Aspool-type flow control valve 47 is axially movable in the valve boreand is urged by spring 48 against a plug stop 49. The valve is providedwith necked portions 50 and 51, communicating respectively at all timeswith inlet and outlet ports 44 and 45, an intermediate sealing land 52,an end sealing land 53, and an end land 54, the latter being providedwith a slight groove or fiat 55 providing communication between theoutlet port 45 and the corresponding end of the valve. Flow controlorifices 56 provide communication from the out let port 45 to theinterior hollow end of the valve and the outlet passage 57 leading topower steering hose fitting 58. As shown in FIG. 5, a power steeringreturn line hose fitting 59 leads directly into the side wall of thereservoir 22 from which free passage into the inlet port 44 is providedthrough passage 60 in the housing extending between the reservoir andvalve bore 46.

A maximum pressure relief valve 61, later described in detail, isadapted to by-pass the power steering pump circuit.

As best shown in FIGS. 2 and 4, the rotor 38 is provided with aplurality of rectangular slots 62 in which U-shaped sheet metal slipperpumping elements 63 are carried and driven by the rotor to provide apumping action between the inlet port 42 and outlet port 43, suchslippers being urged by springs 64 into face engagement with the pumpbore provided by the inner surface of the insert sleeve 30. Such sleeveis locked in correct angular position relative to the housing inlet andoutlet ports 44 and 45 by pin 65. as shown in FIG. 1. It will, ofcourse, be understood that the rotor slots 62 and slippers 63 extendacross the entire width of the rotor and that the rotor and slippers aredimensioned to providel a running pressure sealing fit with the headersurfaces 40, 41.

The general operation of the pump may best be understood by reference toFIG. 2. When the rotor 38 is driven in a counterclockwise direction,hydraulic fluid from the reservoir passes through the passage 60 aroundthe necked portion 50 of the valve 47 through the housing inlet port 44and the sleeve inlet port 42 where it is pumped by slipper elements 63to the outlet port 43 and 45 in the sleeve and housing and through theorifices 56 and outlet passage 57 to the power steering circuit.Pressure in the outlet port 45 oommunicates through flat 55 in the valveend land 54 to the end of the valve exerting pressure against the spring48. Fluid pressure reduced by flow through the orifices 56 operates onthe other end of the valve to assist spring 48 in urging the valve tothe position shown. When a predetermined flow rate through the orificescorresponding to the maximum flow rate demand of the power steeringsystem is exceeded, the pressure differential across the orificesapplied to equal valve end areas overcomes spring 48 causing the valveto shift to a position where direct flow from outlet port 45 at the edgeof land 52 to the inlet port 44 occurs, providing a direct bypass andinjection filling of the inlet port 42. Any pressure demand in the powersteering circuit will be met at the same flow rate up to the maximumpressure established by pressure relief valve 61.

Referring to FIG. 4, the preferred pump bore disclosed is symmetricalabout the center line CL and includes concentric circular arcs a and btangentially joined by tangential circular arcs c, d, c, and d. Typicalvalues for such arcs are (tr-108, bl20, c-30, and d--36, where, as inthe present case, the radius of are a is approximately 85% of the radiusof arc b. The terminal points of the inlet and outlet ports at the boresurface coincide generally with the ends of the arcs a and b with theexception that the inlet port extends into the are d a distanceapproximately equal to the face contact width of one slipper, and intoare [2 a distance approximately equal to one half of such face contactwidth, while the outlet port includes a narrow precompression notch orgroove 70 which extends into are b to a position just short ofestablishing direct communication from outlet to inlet port betweenadjacent slipper sealing edges, thereby providing for gradualpressurizing of the fluid column between adjacent slippers in theworking are.

The slippers are preferably constructed as U-shaped sheet metal elementsformed with an outer central face arc having a radius substantiallyequal to the radius of the working bore arc b with tangential segmentson either side of the central are having a radius substantially equal tothat of the minimum radius bore are 0, so that each slipper ispositioned angularly as Well as radially during their travel in bothworking and sealing arcs by the contact or spanning of a substantialperipheral arc of the bore, while the end 71 of the slipper legs areformed as segments of a common circle having a diameter substantiallyequal to the width of the rotor slot 62 less a slight working clearancewhich will permit the slipper to rock within the slot as required tofollow the contour of the pump bore. A radial slot 72 in the face ofeach slipper provides direct communication between the rotor slot andthe inlet or outlet ports during the slipper travel therethrough and anauxiliary flow passage is provided by a rotor notch 73 extending partway across the lead ing edge of each rotor slot. Such notch may belimited to the width of the port in the insert sleeves 30, which arecentrally located and less than the width of the rotor, leaving acontact surface for the leg of the slipper on either end or, formanufacturing convenience, the notch 73 may start at one side face ofthe rotor and extend part way across, for example, approximately halfway, leaving the remaining half of the rotor slot rectangular forconfining contact with the slipper leg. In either case, it is preferredto limit the notch 73 to a depth such that the leading edge of theslipper leg will not uncover such notch during its travel in the sealingare a but will begin to uncover such notch as it moves radiallyoutwardly in the intake are. This auxiliary filling path, it will beseen provides in combination with the radial slot 72 substantiallyunrestricted flow to the rotor slot under the slipper, thus overcomingany tendency for the slipper to leave the here during high speedoperation as the result of restrictive filling, while not interferingwith the seal developed between the leading legs of each slipper and itsslot during travel in the sealing are. It will be observed from anexamination of the adjacent slippers in the sealing are, as shown inFIG. 4, that at least one full slipper or equivalent portions of twoadjacent slippers will be in sealing engagement with the bore facebetween the inlet and outlet ports at all times, making it unnecessaryfor the rotor itself to form a seal with the bore surface. Such slipperseal construction greatly facilitates manufacturing by eliminating highprecision tolerances for all component dimensions affecting theclearance between the rotor and the rotor bore, selective fitting orother costly alternatives, and also contributes to the feasibility ofthe present blind bore housing construction wherein the concentriccylindrical surfaces 28a, 28b and 28c as well as the header face 40 mayall be finish machined in a single setup, greatly reducing the cost overprevious construction methods.

In insuring adequate slipper sealing between the inlet and outlet ports,the U-shaped sheet metal slipper construction has also been found toprovide an important contributing factor inasmuch as the slippers may beconstructed with suflicient flexibility to permit a slight spreading ofthe legs from internal pressure within the notch as the slipper leavesthe outlet port, thereby reducing the sealing clearances between theslipper legs and the rotor slot during each slippers travel through. thesealing arc. In addition, the relative lightness of weight of thi formof slipper compared to previous solid slipper forms greatly reduces thecentrifugal forces contributing to bore wear.

An alternative slipper construction is shown in FIGS. 6 and 7 wherein anotch 75 is provided in the leading leg of each slipper instead of theradial slot 72. It is preferable in such alternative construction forthe notch to extend all the way up to the contact face as shown in orderto provide a scoop" action in filling the slot during travel through theintake arc. A tangent seal between the rotor and bow is used with thisslipper.

Referring again to FIG. 2, in order to insure quietness of relief valveoperation, the ball check valve 61 is provided with a washer plunger 80which fits closely within the cylindrical bore adjacent the ball seat,the edge of such washer being provided with flats or grooves to limitand control the return rate of the ball to its seat after opening. Theclosely fitting washer bore is limited in depth to permit substantiallyunrestricted outflow when the ball is raised from its seat, therebyoperating only to limit the return rate of the ball to its seat anddampen out hunting action contributing. to noisy relief valve operation.

While a preferred embodiment of the present pump has been describedabove in detail, it will be understood that numerous modifications mightbe resorted to Without departing from the scope of our invention asdefined in the following claims.

We claim:

1. A slipper type pump having a pump bore, a rotor mounted eccentricallyin said bore providing a chamber therebetween, slots in said rotor,slippers carried in said slots adapted to engage said bore throughoutsuccessive portions of said chamber corresponding to a sealing areincluding mini-mum spacing between rotor and bore, an inlet arc ofincreasing spacing, a working arc including maximum spacing, and anoutlet arc of decreasing spacing, and radial inlet and outlet portscommunicating with said bore respectively at said inlet and outlet arcportions of said chamber; characterized by each slipper being formedwith a uniform channel cross section extending throughout its entirelength providing fully open channel ends and a circumferential bore arcspanning outer base face adapted to control the angular as well asradial position of said slipper in its rotor slot, the radially inwardlyextending channel legs of each slipper having outer surfaces dimensionedrelative to the rotor slot with 6 working clearance providing freedom ofangular adjustment and being flexibly spreadable when the effectivepressure internally of said slipper exceeds the effective.

external pressure to effectively reduce said clearance, and said slipperbeing slotted in its bore arc spanning face for registration with saidradial inlet and outlet ports.

2. A slipper type pump as set forth in claim 1 wherein the spacing ofsaid slippers relative to said sealing arc is such that at least oneslipper is interposed in sealing relation with said bore and rotor inthe sealing are between said inlet and outlet ports as well as in theworking arc between said inlet and outlet ports at all times, saidhigher internal pressure being effective to reduce clearance when aslipper is within said sealing arc with the outer surface of the leadingleg exposed to inlet pressure.

3. A slipper type pump as set forth in claim 1 wherein theleading edgeof each rotor slot is notched to provide open flow to the underside ofsaid slipper when it moves radially outward.

4. A pump as set forth in claim 1 wherein said working and sealing arcsare concentric with said rotor, and said inlet and outlet arcs aresmoothly curved to tangentially join adjacent ends of said working andsealing arcs.

References Cited in the file of this patent UNITED STATES PATENTS319,093 Hassinger June 2, 1885 892,443 Ostrander July 7, 1908 2,165,963Curtis July 11, 1939 2,192,588 Heckert Mar. 5, 1940 2,312,886 EllinwoodMar. 2, 1943 2,455,303 Grate Nov. 30,1948 2,499,763 Livermore Mar. 7,1950 2,525,619 Roth et a1 Oct. 10, 1950 2,846,138 Racklyeft Aug. 5, 1958FOREIGN PATENTS 8,123 Great Britain of 1910 31,237 France Sept. 21, 1926110,165 Switzerland May 16, 1925 139,905 Switzerland July 16, 1930286,240 Great Britain Aug. 27, 1927 414,965 Germany June 16, 1925636,513 Great Britain May 3, 1950

